Nickel carbonyl, Ni(CO)4, was first produced by the reaction of metallic nickel with carbon monoxide by Mond in the early part of the 19th century. Today, one of the major industrial processes for making metallic nickel is based on the production of Ni(CO)4 and subsequent thermal decomposition thereof to Ni and CO. One known commercial process operates at about 180° C. and a CO pressure of about 70 atm. It is known that the CO pressure may be reduced when the reactant nickel is catalytically activated.
Activation of the metal has been observed in the presence of mercury (1,2), sulphur in the form of H2S (3,4), hydrogen (5,6) or carbon (7). It has been suggested that the high initial rate of formation of Ni(CO)4 and the subsequent decline to a steady state value is the result of a rapid decrease in the number of activated reaction sites which are produced upon heat treatment of the sample (6,8,9). A study of surface changes during carbonyl synthesis suggests that the maximum rate is associated with fundamental changes in the defect structure. All of the above methods use catalytic activation of nickel in the presence of CO.
Canadian Patent No. 822,016—The International Nickel Company of Canada, published Sep. 2, 1969, discloses a high pressure carbonylation process for particular use with smelter nickel intermediates high in copper and iron.
Methods of reducing mixed metal oxide compositions comprising oxides of nickel, cobalt, copper and iron with hydrogen to produce the respective metals for subsequent nickel carbonylation in the presence of H2S and subsequent decomposition of the nickel carbonyl to metallic nickel in powder or substrate form are known.
However, there remains a need for an improved process of preparing high purity nickel, particularly, nickel powder having acceptable levels of sulphur and metallic impurities, e.g. Co, Cu and Fe.